Electrostatic telephone



J. MASSOLLE ELECTROSTATIC TELEPHONE filed Aug. 5, 1923 April 27, 1926.2, 43

hum v 550/ ,6

Patented Apr. 27, 1926.

UNITED. STATES i,5sz,s4s

PATENT OFFICE.

JOSEPH MASSOLLE, OF IBERLIN-WILMEBSDORF, GERMANY, ASSIGNOR TO TRI-ERGON,

A. G., OF ZURICH, SWITZERLAND, A CORPORATION- OF SWITZERLAND.

ELECTROSTATIC TELEPHONE.

Application filed August 3, 1925. Serial No. 47,661.

To all whom it may concern:

Be it known that I, Josnrn MASSOLLE, citizen of the German Republiresiding at lierlin-lVilmersdorf, Germany, have invented certain new anduseful Improvements in Electrostatic Telephones, of which the followingis a specification.

The electrostatic telephones for trans.- forming alternating electriccurrents with sound characteristics into sound waves, as

h therto used, comprise a rigid capacity body .and an elastic orresilient diaphragm located in close proximity-to the former andconsisting of a mica film or the like with a metallic coating thereon.If electric poten tials are applied intermediate between the rigidcapacity body and thejmeta'llic coating, the distance between thediaphragm and the capacity surface of the rigid body will vary accordingto the degree of applied potential, due to electrostatic attraction and'the movements of the diaphragm will produce sound or acousticvibrations in the surrounding air coupled therewith.

The sound waves should correspond, as regards their curve shape,.asnearly as possible to the fluctuations of the potential. Obviously anyvibrating diaphragm has a series of pronounced resonance notes ortonality and the frequencies corresponding to such resonance notesinvolve 'or produce disproportionately wide amplitudes of the diaphragmand overrun considerably all of the other frequencies.

The object of this invention is to have the form of the curve correspondperfectly;

to the variations of the fluctuations of, ap

plied potential and with this objectin view the distance between thecapacity surface and the diaphragm is made essentially'lss near theperiphery than at the centre so that the diaphragm will be influenced bythe'electrostatic forces with a power gradually increasing in thedirection from the centre towards the periphery. in this way thediaphragm will be eihciently prevented from swinging in pronouncedresonance notes.

With the above recited and other objects in. view, reference is had tothe following specification and to the drawings in which there areexhibited two examples or embodiments-of the invention which are in noway intended as a limitation upon the scope of the appended claims as itis to be clearly BElSS'UEU understood that variations and modificationswhich properly fall within the scope of said claims may be resorted towhen found expedient.

In the accompanying drawings forming a part of this specification Figure1 is a sectional view of one embodiment of the improved electrostatictelephone, and Figure 2 is a similar view showing a second embodimentthereof.

Referring to Figure 1 the diaphragm 1 s peripherically attached to andenclosed in a frame 2. In closeproximity-to the diaphragm but a smalldistance apart therefrom, a rigid capacity body 3 of slightly concave,preferably conical, shape is provided and firmly connected with. theframe 2 by means of screws or the like, as clearly shown. The diaphragmmay consist of a thin sheet of insulating material, such as mica, havinga conductingmetallic coating thereon.-

If a constant electrical potential difference is provided intermediatebetween the capacity surface of the body 3 and the metallic coating ofthe diaphragm, the latter will be bent inwards, upon talking, from theosition'of rest shown in dotted lines at 4, into the position 1 shown infull line. The shape of the capaoity'body or of the active surfacethereof involves that the distance.

between the capacity surface and the diaphragm is substantially lessnear the ,periphery as at 5, than at a central point thereof, as at 6.Consequently the electrostatic forces are substantially more powerfulnear the periphery than near the centre of the intensification of sound.

The capacity body 3 is provided with perforations 8 for the purpose ofreducing the .damfing in the narrow space between thev diap agm and thebody 3. The damping is chiefly produced by or dependent upon thefriction of the air fluctuating on and between the diaphragm 1 and thecapacity surllll face, so that it will be possible to control the aerialfriction and reduce the same to any desired degree by adequatelydimensioning the perforations-8 or selecting the numher and positionthereof.

Referring to Figure 2 showing a modification of the embodiment describedwith reference to Figure 1, 9 designates the diaphragm havinga-metalliccoating, 10 is the frame in which the diaphragm is peripherallyen'closedand 11 is the capacity body. As will be seen in Figure 2 the latter isa} fiat or plane body and not of conical shape as in Figure 1. In thismodification the diaphragm 9 is kept at the desired distance away fromthe body 11 by means of the head 12 of the adjustable central screw, andit is apparent that the said distance can be regulated, as required ordesired, by means of the screw, it being evident that at any suchregulation the distance between the diaphragm 9 and the capacity body 11will invariably be greater at the centre as at 13, than at the peripheryof the parts, as at 14:-

It goes without saying, that the diaphragm may be divided into aplurality of portions or sections or may be composed of several sectionsadapted to be influenced in the manner hereinbeforeexplained andspecifically described with reference to Figures 1 and 2. lln case of adiaphragm divided into or composed of several sections each point orplace where the same are clamped in or otherwise attached to a frame orthe like, will be endowed with the described properties peculiar to theperipheral portion of the diaphragm.

What I claim is;

1. An electrostatic telephone comprising a rigid capacity body and adiaphragm con nected therewith constituting a movable con-- denserplate, the constructionandiarrangement of the parts being such that thedistance between the said body and the said diaphragm is less at theperiphery than at the centre thereof.

2. An electrostatic telephone comprising a rigid capacity body, aresilient diaphragm constituting a movable condenser plate, and meansfor securing said diaphragm in spaced relation to said body, said partsbeing so constructed and arranged as to provide an air gap between saidbody and diaphragn'i of a width decreasing progressively from the centerof the diaphragm and body towards the periphery thereof.

3. An electrostatic telephone comprising 4. An electrostatic telephonecomprising a rigid plate, constituting a capacity body, a resilientdiaphragm extending over said plate, said plate having a centralabutment extending upwardly beyond the adjacent surface thereof, andmeans for securing said diaphragm with its central portion extendingover and contacting said abutmentand its edges secured at a lessdistance from said plate than the distance between the portions of saiddiaphragm adjacent to said abutment, and said plate. i

5. An electrostatic telephone comprising a rigid plate constituting acapacitybody and l a resilient diaphragm constituting a movablecondenser plate held in face to face relation with said rigid plate atdistances between the same which vary, the variation in said distancesbeing adapted to overcome pronounced resonance of said diaphragm whenacoustically modulated electrical potentials are applied between saidrigid and movable plates.

6. An electrostatic telephone comprising a rigid flat capacity body, adiaphragm connected therewith constituting a movable condenser plate,and ameans for adjustably holding the diaphragm a certain distance apartfrom the said body, the said distance gradually increasing from theperiphery to wards the centre of the two parts.

7. An electrostatic telephone, comprising a rigid, plane capacity body,a diaphragm connected therewith, and a screw in the coir tre of the saidbody for adjustably holding the diaphragm acertain distance apart fromthe said body, the saiddistance gradually increasing from the peripheryof the said diaphragm towards the said screw, substan tially as and forthe purpose set forth.

8. An electrostatic telephone, comprising a rigid capacity body, adiaphragm connected therewith, constituting a movable condenser plate,and means for holding the latter firmly connected with the said body ata varying distance apart from the same, said rigid body havingperforations therethroug J MASSULLE.

Bil

